Oil-pump with a pressure-regulating valve connected on the outlet side

ABSTRACT

The invention relates to an oil-pump assembly which includes a pressure-regulating valve. The object of the invention is to remove air and oil from the spring chamber of the pressureregulating valve. The shaft seal chamber has a slide-ring seal attached to the pump shaft which operates as a check valve. The pump casing is formed so that the shaft seal chamber has fluid communication with the shaft bore, the suction inlet of the pump and the spring chamber of the regulating valve. The shaft seal functions as a check valve which opens when pressurized oil from the pump discharge flows outwardly through the shaft bore. The mouth of the passage leading to the spring chamber of the pressure-regulating valve is opened or closed depending on the axial position of the shaft seal and when the mouth is open, air and oil is drawn from the regulating valve spring chamber to the suction inlet of the pump through the shaft seal chamber.

iJite tea diet 2,960,112 11/1960 Lipinski Inventors Gunner LyshojHansen;

Jorgen lllartvig Petersen, both of Nordborg, Denmark Appl. No. 847,582Filed Aug. 5, 1969 Patented Nov. 2, 1971 Assignee Damfoss A/S Nordborg,Denmark Priority Sept. 17, 1968 Germany OIL-PUMP WITH APRESSURE-REGULATING VALVE CONNECTED ON THE OUTLET SIDE 3,363,577 1/1968i-leijnis Primary Examiner-Robert M. Walker Attorney-Wayne B. EastonABSTRACT: The invention relates to an oil-pump assembly which includes apressure-regulating valve. The object of the invention is to remove airand oil from the spring chamber of the pressure-regulating valve. Theshaft seal chamber has a slide-ring seal attached to the pump shaftwhich operates as a check valve. The pump casing is formed so that theshaft seal chamber has fluid communication with the shaft bore, thesuction inlet of the pump and the spring chamber of the regulatingvalve. The shaft seal functions as a check valve which opens whenpressurized oil from the pump discharge flows outwardly through theshaft bore. The mouth of the passage leading to the spring chamber ofthe pressure-regulating valve is opened or closed depending on the axialposition of the shaft seal and when the mouth is open, air and oil isdrawn from the regulating valve spring chamber to the suction inlet ofthe pump through the shaft seal chamber.

OIL-PUMP WITH A PRESSURE-REGULATING VALVE CONNECTED ON THE OUTLET SIDEThe invention relates to an oil-pump with a pressure-regulating valveconnected on the outlet side and a shaft seal in the form of aslide-ring seal, and in which a backing member, rotatable with theshaft, bears resiliently against an inner end wall of the housing, andleakage oil is passed along the shaft and through the gap between thebacking member and the end wall into a housing chamber containing theslide ring, a chamber in the pressure-regulating valve being incommunication with the suction side of the pump by way of a pathcontaining a check valve, which path passes through the housing chamber.

Pressure-regulating valve must normally have a connection with thesuction side so that oil that penetrates into zones where it is notrequired during operation can be discharged therefrom. This appliesparticularly in the case of the chamber behind the control piston, sinceoil that collects there would adversely affect the performance of thepressure-regulating valve. n the other hand, however, this chamber caneasily become filled with air during the standstill periods, since themovable seals provided for the oil offer only slight resistance to theair. If, when the pump starts up, this air is passed to the suctionside, the pump delivers air, at least in part, instead of oil, and thenecessary oil pressure can only be built up slowly if at all. In theextreme case, the oil-pump circulates only air through thepressure-regulating valve; it then functions to some extent in shortcircuit.

To remedy this defect, an arrangement has been proposed in which thestated chamber in the pressure-regulating valve communicates, by way ofa passage, with the housing chamber for the slide-ring seal, and thiscommunicates with the suction side of the pump by way of a check valvewhich only opens when a predetermined pressure differential occurs.Since such pressure differential can only occur if the pump hasdelivered a sufficient quantity of oil, the air contained in thepressureregulating valve does not interfere with the starting-upprocess.

There are of course difficulties in designing the check valve tofunction correctly. On the one hand a large closing pressure andtherefore a strong valve spring are required in order to close the checkvalve tightly in all conditions and also to provide an effective checkto the air. On the other hand, the force required for opening must notbe too great and the valve spring should not therefore be too strong,since the pressure permissible in the housing chamber is limited onaccount of the tightness of the pump.

The object of the invention is to design an oil-pump of the simplestpossible construction in such a way that, on the one hand, the checkvalve can be kept closed by an adequate closing pressure, while on theother hand impermissibly high-pressure levels do not occur in thehousing chamber.

According to the invention this object is achieved by causing thebacking member, displaceable when leakage oil occurs, to control thecheck valve.

Leakage oil only occurs to any appreciable extent if the pump generatesa considerable pressure, i.e. when it delivers oil, in the main, and noair. The leakage oil acts over a relatively large area of the backingmember and therefore applies considerable forces to this member. Theseforces are so great that they are able to influence the relativelystrong spring of the slide-ring seal. If therefore, in accordance withthe invention, this backing member is used for controlling the checkvalve, sufficiently great forces are available for the openingoperation; the check valve can therefore be kept closed with a largeclosing force. Moreover, this control arrangement becomes automaticallyeffective only when the pump is running at speed and is deliveringsufficient oil. The pressure in the housing chamber can nevertheless bekept at any level, even a low level if required, since this chamber cancommunicate directly with the suction side or a point of definitepressure in the pump, e.g. with a certain chamber defined by teeth.

Here, it is particularly advantageous if the backing member is firmlyconnected to the closure member of the check valve.

In this case, the spring of the slide-ring seal simultaneously acts as avalve spring, so that its relatively great force can be used as theclosing force.

Furthermore, it is also advantageous if the sealing surface of the checkvalve is formed between the backing member and the end face. The backingmember then forms the closure element of the check valve and the innerend face of the housing constitutes the valve seat. In this manner acheck valve having good functional properties is obtained by usingcomponents already present.

In a preferred embodiment, the passage leading from thepressure-regulating valve to the housing chamber terminates in the pathof the leakage oil in the direct vicinity of the backing member. At thispoint, the pressure of the leakage oil has already relaxed to a largeextent, so that a lower pressure obtains, as required, in the adjoiningchamber of the pressureregulating valve.

The invention will now be described in more detail by reference to anembodiment illustrated in the drawing, in which:

FIG. 1 shows the connection diagram of a pump that can be equipped inthe manner proposed by the invention, and

FIG. 2 is a longitudinal section through an embodiment of the invention,the passages of importance to the invention being turned to bring theminto the plane of the section.

Referring to the diagram seen in FIG. I, an oil-pump I draws oil from asump 3 by way of a suction pipe 2 and delivers it through a pressurepipe 4 to a pressure-regulating valve 5 and, through a nozzle pipe 6 toa fuel-oil nozzle 7. The pump is powered by a single-phase asynchronousmotor 8 through a shaft 9, which extends through a sealing device 10incorporating a slide-ring seal. The pressure-regulating valve 5,illustrated in a much simplified manner in the drawing, has a piston 11,which in the at-rest position blocks the inlets to the nozzle pipe 6.When the pressure in the pressure pipe 4 rises, the piston 11 isdisplaced, overcoming the pressure of a spring 13, adjustable by meansofa set screw 12, and an edge 14 of the piston thereby uncovers anorifice 15 to a greater or lesser extent. Consequently, surplus oilflows through a section 16 of the pipe. The chamber 17 behind the pistonis connected by a pipe 18 to the pipe 16. The pipe 16 leads to theinterior of the sealing arrangement 10 by way of a check valve, notillustrated in FIG. 1. From this sealing arrangement, a return pipe 19leads, on the one hand, through a section 20 to the suction pipe, and,on the other hand, through a section 21 to the sump. The parts containedin the rectangle 22, shown in broken lines, are accommodated in a commonhousing which is represented by the housing 30 and cover 31 of the unitshown in FIG. 2.

In the form of construction shown in FIG. 2, the pump has an innertoothed wheel 23, which is firmly connected to a shaft 24 (correspondingto shaft 9 in FIG. 1) so as to rotate therewith, and an internallytoothed ring 25, which is able to rotate in the fixed housing 26. Theparts 23, 25 and 26 are covered by an end-plate 27, in which areprovided distributing grooves etc. The parts 23, 25, 26 and 27 whichcorrespond to the pump 1 of FIG. 1, are held on the end-face 29 with thehelp of screws 28. This pump arrangement is covered by its own cover 31,which surrounds a suction chamber 32. Contained in this suction chamberis a screen 33, one edge of which engages in an annular groove 34 in theend-face 29 of the housing, and the other edge of which extends into aseal 35, which is formed on the circumference of a resilient disc 36.The space 37 between the disc 36 and the cover 31 is filled with air andacts as a shock-absorber. The suction chamber 32 is connected by way ofpassages, not illustrated, to a port, to which is connected section 2 ofthe suction pipe of FIG. 1.

The shaft 24 is mounted in two bearing bushes 38. which are fitted in alongitudinal bore in the housing 30. At that side opposite the end-face29, the housing 30 contains a chamber 39 which accommodates a slide-ringseal which corresponds to the sealing device 10 of FIG. 1. Theslide-ring seal comprises a slide-ring 40, rotating with the shaft, anda fixed face-ring M.

The latter is held in position by means of a circlip 42 and is pressedby a corrugated spring 43 against an annular surface 45 on the end faceof the chamber 39, an O-ring 44 being thereby compressed. Mounted on theshaft 24 to rotate therewith is a backing member 46 which serves tosupport a spring 47, which applies an axial pressure on the slide-ring40 by way of a washer 48. The slide-ring is also coupled, by way of thespring 47 and fingers on the washer 48, with the backing member 46 togive a rotary drive. When the equipment is in operation, a floatingbearing is formed between the inner endface 49 of the housing and thebacking member 46, since leakage oil emerges from the pump and flowsalong the shaft 24 which corresponds to the shaft 24' of FIG. 1, intothe chamber 39. For this purpose, axial grooves can be provided in thebearing bushes 38 or in the bore of the housing in which they areaccommodated, as shown in broken lines on the exterior of the bearingbush at 50, and on the interior of the bearing bush at 51.

The housing also contains a bore 52 which accommodates the moving partsof a pressure-regulating and cut-off valve, which is the valve assemblyof FIG. 1. From this bore 52 runs a passage 53, at the correctfunctional level of course, and this passage, which corresponds to thepipe 16 of FIG. 1, terminates at the point 54 near the end of theleakage oil path, in this instance therefore at the end of thelongitudinal bore in the housing 30. A further passage 55 whichcorresponds to the pipe 19 of FIG. 1, leads from the housing chamber 39to the annular groove 34 in the Suction chamber 32.

When a pump of this kind is set in operation, if there is directcommunication between the bore 52 and the suction chamber 32, therewould arise the danger that the pump, instead of delivering oil andbuilding up a pressure, would suck air from the bore 52 and, due to thelow resistance to air in the pressure-regulating valve would deliver inthat direction again,

by short circuit so to speak. In the present case such directcommunication is not possible, since the backing member 46, acted uponby the pressure from the strong spring 47 and bearing against theend-face 49, acts as a check valve. However, as soon as the pumpdelivers oil and sets up a certain pressure, leakage oil passes outwardsalong the shaft 24 and, as soon as it reaches a certain pressure,removes the backing member 46 from the end-face 49. Thus, not only is afloating bearing created, but also a passage for the medium to bedischarged from the bore 52 i.e. oil primarily but initially air aswell.

We claim:

1. An oil-pump assembly comprising a casing, a suction inlet chamber, apressure-regulating valve having a spring chamber, a shaft bore in saidcasing, a pump shaft rotatably journaled in said shaft bore, said casinghaving a shaft seal chamber adjoining said shaft bore, said shaft sealchamber having a wall with a sealing seat formed thereon, a slide-ringseal in said shaft seal chamber including resilient means axiallybiasing said seal against said seat, said casing having first passagemeans between said valve spring chamber and said shaft seal chamber,said passage means having a mouth within the confines of said seat sothat the egress of fluid from said passage means to said shaft sealchamber is controlled by said slidering seal, said casing having secondpassage means between said shaft seal chamber and said oil pump suctioninlet chamber.

2. An oil-pump pump assembly according to claim 1 wherein saidslide-ring seal includes a backing member attached to said shaft forrotation therewith and axial movement relative thereto.

3. An oil-pump assembly according to claim 2 wherein said spring chamberis formed in said casing.

1. An oil-pump assembly comprising a casing, a suction inlet chamber, apressure-regulating valve having a spring chamber, a shaft bore in saidcasing, a pump shaft rotatably journaled in said shaft bore, said casinghaving a shaft seal chamber adjoining said shaft bore, said shaft sealchamber having a wall with a sealing seat formed thereon, a slide-ringseal in said shaft seal chamber including resilient means axiallybiasing said seal against said seat, said casing having first passagemeans between said valve spring chamber and said shaft seal chamber,said passage means having a mouth within the confines of said seat sothat the egress of fluid from said passage means to said shaft sealchamber is controlled by said slide-ring seal, said casing having secondpassage means between said shaft seal chamber and said oil pump suctioninlet chamber.
 2. An oil-pump pump assembly according to claim 1 whereinsaid slide-ring seal includes a backing member attached to said shaftfor rotation therewith and axial movement relative thereto.
 3. Anoil-pump assembly according to claim 2 wherein said spring chamber isformed in said casing.